Conventionally, as a polymerization method for a polymer comprising a polyvinyl ether structure, a polymerization method by living cationic polymerization has been known (see, for example, Japanese Unexamined Patent Application Publication Nos. H11-080221A and 2007-099881A).
As the polymerization method for a vinyl ether monomer, cationic polymerization is common as described in Japanese Unexamined Patent Application Publication Nos. H11-080221A and 2007-099881A, and the like, and radical polymerization has been regarded as being extremely difficult according to the knowledge of polymer synthesis hitherto.
Further, as a vinyl ether polymer obtained by polymerizing a vinyl ether monomer, molecular weight distribution (Mw/Mn) serving as the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) is preferably narrow from the viewpoint that the polymer is capable of structural control, resulting in more stable mechanical properties as a polymer. Specifically, the value of the molecular weight distribution is preferably less than 2.0, and more preferably approximately 1.5 or less.